Numerical Solution Techniques for Reaction Parameter Sensitivity Coefficients in Multi-component Sub-surface Transport Models (HES 59)

United States Department of Energy, Subsurface Science Programunpublishednot peer reviewe

Numerical Solution Techniques for Reaction Parameter Sensitivity Coefficients in Multicomponent Subsurface Transport Models

203 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1998.For reactive transport, the state equations consist of a nonlinear PDE for each aqueous component and a nonlinear ODE for each immobile component; these differential equations are coupled together through reaction source/sink terms. The corresponding sensitivity equations take the form of a system of linear PDEs and ODEs. Codes are developed to compare the practice of solving the entire system of sensitivity equations to applying the operator splitting approach to solve the sensitivity equations. Codes are also developed to compare the direct and adjoint methods of calculating reaction parameter sensitivity coefficients in batch and transport problems. CPU time comparisons for example transport problems indicate that direct calculation of sensitivity coefficients is much more efficient than the calculation of sensitivity coefficients by direct perturbation. These comparisons also demonstrate that operator splitting results in a significant reduction in simulation time. Reaction parameter sensitivity coefficients are calculated for a series of example transport problems. These examples include a cobalt-NTA problem with kinetic sorption and biodegradation and a uranium-quartz system with mass transfer-limited surface complexation reactions. The computed sensitivity coefficients are used to gain insight into the relative significance of reaction processes and to rank individual reaction parameters in terms of importance. Sensitivity coefficients are also used to quantify the degree of coupling between components.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Numerical Solution Techniques for Reaction Parameter Sensitivity Coefficients in Multicomponent Subsurface Transport Models

203 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1998.For reactive transport, the state equations consist of a nonlinear PDE for each aqueous component and a nonlinear ODE for each immobile component; these differential equations are coupled together through reaction source/sink terms. The corresponding sensitivity equations take the form of a system of linear PDEs and ODEs. Codes are developed to compare the practice of solving the entire system of sensitivity equations to applying the operator splitting approach to solve the sensitivity equations. Codes are also developed to compare the direct and adjoint methods of calculating reaction parameter sensitivity coefficients in batch and transport problems. CPU time comparisons for example transport problems indicate that direct calculation of sensitivity coefficients is much more efficient than the calculation of sensitivity coefficients by direct perturbation. These comparisons also demonstrate that operator splitting results in a significant reduction in simulation time. Reaction parameter sensitivity coefficients are calculated for a series of example transport problems. These examples include a cobalt-NTA problem with kinetic sorption and biodegradation and a uranium-quartz system with mass transfer-limited surface complexation reactions. The computed sensitivity coefficients are used to gain insight into the relative significance of reaction processes and to rank individual reaction parameters in terms of importance. Sensitivity coefficients are also used to quantify the degree of coupling between components.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Concentrations and Estimated Loads of Nitrogen Contributed by Two Adjacent Wetland Streams with Different Flow-Source Terms in Watkinsville, Ga.

Proceedings of the 2007 Georgia Water Resources Conference, March 27-29, 2007, Athens, Georgia.Inorganic, fixed nitrogen from agricultural settings often is introduced to first-order streams via surface runoff and shallow ground-water flow. Best management practices for limiting the flux of fixed N to surface waters often include buffers such as wetlands. However, the efficacy of wetlands to immobilize or reduce nitrate depends on several interacting local conditions that are not well understood. Two adjacent streams (14 m apart at source) draining a wetland depression have partly different flow-source terms. One has a flowing spring at its head-cut, and is protected by surface runoff by a man-made berm. The other accepts run-off from the upland pasture and does not have a conspicuous spring. The lower discharge and higher organic substrate, residence times and water/sediment contact all apparently contribute to the lower nitrate loads from the runoff stream.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, Natural Resources Conservation Service, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1990 (P.L. 101-397) or the other conference sponsors